A bare die is usually packaged before it is suitable for connecting to a circuit board. A common technique for packaging die is wire bonding, in which a fine wire provides a connection between a contact site on a die and a contact site on a substrate. The substrate may be the ceramic base of a package, an organic laminate or another chip. When wire bonding is used, the connection sites must usually be near to the periphery of the die, and are usually limited to one or two rows of contacts. This places a limit on the minimum size of the die, which can become problematic when the number of contacts is large.
A recently developed technique for packaging die involves embedding the die, for example in an organic laminate. An advantage of using embedded die is that connections from the die are no longer limited to being near its periphery, so the size of the die can be decreased for a given number of contacts.
WO 2004/077903 describes an electronic module that includes a component, such as a die, embedded in a laminate. The die is surrounded by an insulator. Contact sites on the die are connected to a conductive layer pattern on one of the outer layers of the laminate by means of conductive pathways running through the insulator. Array-type connections can be made on the die.
When there are several dice, current techniques involve arranging bare dice side by side on a common substrate. The combined package is known as a multi-chip module (MCM). The bare dice can be bonded to a substrate using wire bonding or tape-automated bonding and interconnected. Alternatively, the dice can be embedded in a laminate and connected to one another using vias. An advantage of using MCMs is that signal delay due to the length of connections between the dice is minimised.
WO 2005/027602 describes an electronic module comprising three components, such as dice, embedded within a laminate. Conductive patterns within the laminate connect the required contacts on each die to contacts on the other dice.
Another technique for providing multiple dice in a package is three dimensional packaging technology. In these packages, the dice are stacked on one another. If the dice are to be wire-bonded, the dice are stacked in size order with the smallest on top. Again, peripheral connection sites are preferable. This provides a package with a much smaller footprint than a two dimensional package, and thus a much larger silicon efficiency than MCMs. Another advantage is that the length of the interconnections between the die can be much shorter than in MCMs. However, the total thickness of the die increases. In addition, the manufacturing process can be more complex than for MCMs.
U.S. Pat. No. 6,861,366 describes a packaged semiconductor device that includes two dice. The first die is attached to a substrate, and wire bonds connect the contacts on the first die to contacts on the substrate. An encapsulant extends over the first die and its wire bonds. The second die is stacked on top of the encapsulant, and also has wire bonds connecting its contacts with the contacts on the substrate. The second die and its wire bonds are also covered with an encapsulant.